Almost any mechanical device contains hollow shapes, such as tubes, shafts, shells, housings and the like. Such features as the ability to contain and guide liquid streams, minimal weight-to-strength ratio, etc. make these parts indispensable in the design of practically any mechanical device or system. It has long been a goal of manufacturers to improve geometry, precision, and mechanical properties of hollow parts since to do so would enhance energy efficiency and reliability of a number of devices. Such improvements would be especially valuable and important for the aerospace industry where weight minimization is one of the key objectives of aircraft design. However, in many cases the geometry and material choice of hollow parts are determined by the cost of fabrication rather than design optimization. Currently, deformation of hollow objects is commonly carried out by the use of hydroforming and explosive forming. Despite several obvious advantages, these processes have their shortcomings.
Hydroforming is a quasi-static process that changes the shape of a hollow part without significant expansion of the part. The drawbacks of the hydroforming process include unpredictable wall thinning in die corners, insufficient dimensional repeatability, lack of concentricity, and work hardening. These features impede process applications for forming repeatable, precise, and structurally sound expanded components. Moreover, to obtain expansions in the range of 20%, an axial tube feed is required. Another significant obstacle preventing wide adoption of a hydrostatic expansion technique is the high capital cost of forming equipment (pumps, presses, etc.).
Explosive forming is a high energy rate process that became established in the metal forming industry in the 1960s and 1970s. The method has been especially useful in the aerospace, gas turbine, and nuclear industries. The need for large components, produced in small runs and within short lead times, has been the driving force behind the development of this method. The main disadvantage of explosive forming is the lack of ability to produce small, precise, or large manufacturing volume parts. Moreover, the technology must be handled by well trained personnel and in remote facilities.
Thus there is a need in the art for systems and processes which overcome the deficiencies of traditional hydroforming and explosive forming techniques.